I have a EFLU2680 F4U Corsair which has flown for a total of about 45 min max. I use a DX7 Tx on DSMX protocol. No crashes or mishaps.

Problem: the prop does not rev up to full power.

Yesterday I flew in fairly high winds and used full power for much of the flight time. I had used four 160 mAh batteries in rapid succession and ½-way through the last flight the plane lost power - it dropped down to just under ½ throttle. The power was just enough to keep the plane floating in the air but due to the wind gusts I had to land. I switched to a fresh battery but the problem remains

The prop spins freely and nothing is bent or out of shape mechanically. The batteries are fine. The motor seems to run fine but I can't get more revs than what correponds to a about a ½ throttle setting.

What should I suspect? The motor? The ESC?If it is the ESC, do I need a complete new Rx board with ESC & servos?

Did you allow any time for cool-down between flights? The reason I ask is because you said "in rapid succession". Even these small park fliers generate a lot of heat. You may have overheated the esc or the motor.

Hello and thanks for your response. Yes, that's what I was thinking too and no, I did not leave time for cool-down. A lesson learned I guess....
I'll open the the fuselage and check these components. If I'm lucky it's just the motor, but I guess the esc will tend to fry first?
Also next time I fly I'll bring two or more planes and alternate between flights. Thanks again for your input

I would suspect either the motor or possibly the gearbox. Check the gearbox shaft and make sure there is no slop or a slipping gear. Change out the motor next. The last suspect item would be the receiver/esc board.

Thanks Brian, good tips, will check all those things. I flew without landing gear over tall grass and had one quick and unscheduled arrival after a sudden wind gust. No harm to the plane, but I guess there can be a lot of strain on the drive train when the prop stops abruptly like that. It sure would be nice if the Rx/esc board is OK
/Tomas

You are welcome. Always glad to help. Of course, the harder you fly (full throttle), the more current you draw, the more heat you generate. Makes sense, right? I usually like to take a little break between flights, gather my wits, as it were. I'm flying bigger, glow powered stuff I built myself so I need to be more aware of things in general. It's a lifetime of learning and I love it! "Bashing balsa since 1979"

Thanks Brian, good tips, will check all those things. I flew without landing gear over tall grass and had one quick and unscheduled arrival after a sudden wind gust. No harm to the plane, but I guess there can be a lot of strain on the drive train when the prop stops abruptly like that. It sure would be nice if the Rx/esc board is OK
/Tomas

You're welcome. Rarely does a esc fail only allowing half throttle. These boards will fail if they get wet or if the prop is jammed while full throttle is on for a long time. My money is on the motor.

I opened the fuselage hatch today after work and checked the components. The motor ran erratically and didn't rev up. I then unplugged the motor and plugged in a spare motor +plus gearbox +prop for a different plane that I borrowed from a friend.
Guess what? That spare power unit ran perfectly, so the ESC is definitely OK.
Now I'll order the correct power unit for the Corsair and it should be up in the air soon, with a minimum of expense.
Thanks again guys for your input - I learned a lot from this experience.

I finally received a new motor for the UMX F4U via eBay, it took a little while.
The RX/ESC/servo board had to be lifted up from its seat to make room for the motor as it was pushed back out from the gearbox, but that was easy. There was just a tiny string of glue on either side along the board and it lifted up easily with minimumum damage to the foam seat.
God thing I didn't have to remove entire gear box - that would have been a lot more difficult, with damage the foam seating.
The new motor revs as it should and spins the prop with loads of power, so we're back in business...Nice!

One thing I noticed with the hot glue - the nozzle tends to leave a thin trail of glue, like a thread as it is lifted away from the puddle that you deposit. One such thread landed on a servo output gear and messed up the gear mesh badly. It took quite a bit of work with a loupe and the tip of an scalpel blade to sort that out.
The original glue is white, opaque and very elastic. Does anyone know what it is, and where to get it?